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leoswift9

Citan O2 sensor issues

My 2012 Mercedes Citan with a diesel engine is throwing codes related to the O2 sensor. The check engine light is on, and I'm seeing a drop in fuel efficiency. I suspect the catalytic converter is working overtime because of this. Has anyone else dealt with a dodgy O2 sensor on their Citan? I've checked the sensor itself, and it seems okay, but I'm wondering if it's a cable or plug connection that's causing the issue before I consider replacing the O2 sensor. Any thoughts?

Summary of the thread

A 2012 Mercedes Citan with a diesel engine was experiencing issues related to the O2 sensor, indicated by a check engine light and reduced fuel efficiency. The initial suspicion was a faulty O2 sensor or a catalytic converter issue. However, upon inspection, the problem was traced to a corroded plug connection in the wiring harness. Cleaning the connection and replacing the connector resolved the issue, restoring normal function and fuel efficiency.

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4 comment(s)

liamlion1

I had something similar happen on my Citan. Check the wiring harness connected to the O2 sensor. Is it visibly damaged or corroded? I'm not a mechanic, but that was the culprit for me. What's the error code?

leoswift9 (community.author)

I'll check the wiring harness super closely tomorrow. When you say 'similar,' do you mean exactly the same symptoms – check engine light, fuel efficiency tanking, and O2 sensor code? Was it a pain to get to the wiring?

liamlion1

Yeah, pretty much the same. Light on, fuel consumption went up. I didn't mess with it myself, just took it to a workshop. They sorted it quickly. Might be worth doing the same, just to be safe.

leoswift9 (community.author)

Turns out you were spot on. I checked the wiring harness, and the plug connection was indeed corroded. I cleaned it up as best I could, but in the end, I took it to a local shop. They replaced the connector and did a diagnostic check. Total cost was 95€. Check engine light's gone, and the fuel efficiency seems to be back to normal. Fingers crossed it stays that way!

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MERCEDES

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CITAN